How could I know if there's a keylogger in my system, or at least if one is active right now?
Is a keylogger running right now?
Did I accidentally download a trojan/virus keylogger?
What if I'm on an "untrusted" Ubuntu system?
So what if you're in an internet/cybercafe, at the library, at work, etc.? Or even a home computer used by many family members?
Well, all bets are off in that case. It's fairly easy to spy on your keystrokes if someone has enough skill/money/determination:
So, the best you can do with an untrusted system is to take your own Live-CD/Live-USB and use that.
Yes, Ubuntu can have a key-logger. Its far fetched, but it can happen. It can be exploited via a browser and an attacker can run code with your user privileges. It can use auto-start services which run programs on login. Any program can get scan codes of pressed keys in X Window System. It is easily demonstrated with
linux key loggers needs to have a root access before they can monitor the keyboard. unless they don't gain that privilege they can't run a key logger. The only thing that you can do is check for rootkits. To do that you can use CHKROOTKIT